Ulrich,
You are getting the best advice from the best people. Mark, Sean, James and Duncan are the best, not only knowledgeable but just great guys!! I don't think you can go wrong with any of ideas.
That Heathlands Challenge (Notts, Sherwood Forest, Lindrick) is really intriguing and a great deal but is a bit of driving. Reddish, Delamere, Cavendish (and a round at Wilmslow) is terrific and with the guys you would be playing with is just an outstanding way to enjoy a trip. And Manchester airport is terrific and this would be easy driving. And Little Aston, Beau Desert and Whittington Heath (which I have not yet played) would be a lot of fun and it is great golf. And if you fly into Brimingham is very convenient and easy driving.
I just do not think you can go wrong with any of those. They are a bit different but all terrific. Each are special in their own ways. And the guys you'll meet are the best. IF there is any way to get them all in by lengthening the trip that would be the best. If I flew over the Atlantic just to play those courses mentioned I would consider it a fantastic golf trip and would leave England very happy.
Enjoy your trip!!